import java.util.HashMap;

// Using HashMap
// with a key with no hashCode or equals over-riding
public class Test {

  public static void main(String[] args) {
    HashMap<MyClass, String> map = new HashMap<>();
    MyClass a = new MyClass(1);
    MyClass b = new MyClass(2);
    MyClass c = new MyClass(3);
    map.put(a, "One");
    map.put(b, "Two");
    map.put(c, "Three");
    String str = map.get(a);
    System.out.println(str); // One
    map.put(b, "Change"); // update value of key b
    str = map.get(b);
    System.out.println(str); // Change
  }
}

class MyClass // key class
{

  int x;

  MyClass(int x) {
    this.x = x;
  }
}